Dimensional Analysis of Selected Linear and Curved Measurements of Human and Baboon Brains

Research Article

Austin J Nurs Health Care. 2015;2(1): 1013.

Dimensional Analysis of Selected Linear and Curved Measurements of Human and Baboon Brains

Pokhariyal Ganesh¹*, Hassanali Jameela², Ndungu Michal³ and Kimani Njoki³

1School of Mathematics, University of Nairobi, Kenya

2School of Medicine, Department of Human Anatomy, University of Nairobi, Kenya

3Institute of Primate Research, National Museums of Kenya

*Corresponding author: Ganesh Pokhariyal, School of Mathematics, University of Nairobi, Kenya

Received: February 11, 2015; Accepted: April 07, 2015; Published: April 17, 2015


Brains of primates show morphometric differences that may be influenced by the process of functional complexity, evolution and adaptation. Comparative topographic measurements of the primate brains have been used to explain functional and evolutionary trends between the species and to highlight differences in salient functions. Variations in selected linear measurements of the human and baboon brains have demonstrated functional complexity. Some neuro-pathological conditions of the brain may show characteristic morphometric changes. Selected dimensional linear and curved measurements of 4 human and 4 baboon brains from the superior, inferior and lateral aspects were analyzed using ratios to evaluate variability in the morphology of the brains. The ratios for the same species (linear vs curved) provide the extent of the curvature on that measurement. This could be interpreted that more curving suggests more neurons and greater volume. With inter-species ratios; a bigger value implies a higher density of neurons or greater volume for the aspect under consideration. Intra-species co-efficient of variation comparison indicates that curved measurements had a higher variability than the linear in both species. Comparison of symmetry in terms of ratios of both linear and curved measurements indicated no significant difference between hemispheres for both species. There was similarly no significant intra-species difference in terms of curvature between the left and right aspects, but the measurement landmarked by summit of central sulcus and inferior temporal gyrus showed the highest difference in curved measurements. This study provides baseline data for certain morphometric measurements that may be used to assess pathological changes in brain disorders as found in imaging studies. Ratios may also be used to show structural, functional and evolutionary differences and trends between primate brains.

Keywords: Linear; Curved; Measurements; Analysis; Human; Baboon brains


The purpose of this study was to compare the brain parameters of human and baboon brains. The linear and curved measurements from the superior, inferior and lateral aspects were analyzed using various ratios to study variability in the morphology of human and baboon brains. Studies comparing body size, body weight and cranial capacity of hominids show that brain size correlates isometrically with body size [1-3]. Morphological variations in the primate brain reflect functional complexity, evolutionary trends with respect to body size and functional adaptations [4-7]. Body size and weight have been associated with the size of the brain and its components, but this has not been addressed explicitly [8,9].The parameters of the various parts of the cerebral hemisphere may show differences that reflect their functional aspects between and within species [9]. Comparative analysis of human and baboon cerebral linear measurements has demonstrated morphometric differences between the two species [10]. Linear brain parameters have been used in regression models to predict body weight and height [11]. Morphometric equations have been used to predict body weight for large bodied mammals such as polar bears in wildlife research, which would otherwise be difficult using direct scale weighing of individuals [12].

Studying brains in evolutionary contexts requires examination of large numbers of specimens and species, and all major parts of the brain. Thus; evolutionary studies of many species and of whole brains still tend to be based upon simpler data, such as sizes of brains and brain components [13]. Deacon’s replacement hypothesis indicates that changes in the amount of connectivity within a system results in correlated reorganization of circuitry, producing plasticity changes that are species specific [14]. Several morphometric parameters are considered to be important for understanding the relationship between various parts of the cerebrum [7]. Recent reports indicate that humans and apes show consistently different brain morphologic parameters [15]

The present study analyzed ratios of selected linear and curved measurements in the brains of humans and baboons with a view to elucidate differences in functional and evolutionary aspects of the brains. The ratios of curved and linear measurements would indicate differences in the volume of the selected brain parameters. The baseline data obtained could be used as a reference to compare with morphometric changes with brain anomaly seen in functional imaging and Magnetic Resonance Imaging (MRI) [16,15].

Materials and Method

Human brains

Four formalin fixed whole adult human brains of unknown sex were obtained from the Department of Human Anatomy, University of Nairobi. The brains were harvested from bodies obtained for educational purposes, as per the Human Anatomy act (2008). The bodies were fixed by perfusion with 10% formalin. The average body weight for humans was used (65 kg). Each of the brain was given an index number 1 to 4.

Baboon brains

Four whole formalin fixed Olive baboon brains were obtained from the Institute of Primate Research, National Museums of Kenya. The available baboon brains were all male, from a feral troop trapped from Tinga, Kajiado district and subsequently taken through a 90 day quarantine period at the Institute. During this period the animals underwent a general physical examination, screening for infectious agents, de-worming and testing for tuberculosis, prior to allocation to experimental groups. The four baboons were mature adult males designated Pan 2921, 2924, 2927 and 2929 with body weights ranging from 23.3 to 26.5 kilograms.

The four baboons were sacrificed due to old age, oral and other pathologies and the brains harvested. Firstly, the animals were sedated with a ketamine/Xylazine mixture of the ratio 10ml of 10% ketamine/2.5ml of 2% xylazine at the dose rate of 1ml of mixture/10kg body weight and then sacrificed with an intravenous dose of Euthatal® (20% pentobarbital) at 0.5 mg/kg, then followed by trans-cardiac perfusion through the left ventricle using 10% formalin. Whole brain was then harvested and preserved in 10% formalin. The human and baboon brains were weighed using a weighing scale. Ethical approval for the study was granted by the Institutional Review Committee.

Topographic measurements

Linear and curved topographic measurements of the brains from superior, lateral and inferior aspects in coronal or sagittal plane were carried out as described. Three observers carried out the measurements in terms of the superior, inferior and lateral perspectives of whole brains either as coronal, or sagittal, linear or curved measurements and the means from the three readings were obtained. The reference points for the selected linear and curved measurements were established by the three observers who carried out the measurements after repeated standardization. Inter and intra observer errors were less than 5%. All measurements were done using a flexible metric tape and vernier calipers to the nearest millimeter.

The legend and illustrations below describe the linear and curved measurements taken from the three aspects using the reference points (Figures 1, 2 and 3). Linear distances are shown by a solid line and curved by a broken line. The following linear and curved measurements were taken in sagittal and coronal planes. Measurements were carried out on right (Rt) and left (Lt) hemispheres. (Figure 1, 2 and 3).